http://images.lowes.com/product/026715/026715153336.jpg
I've wondered about something like that for years.
Daydreaming of something like this,I wanted to buy one of these and run it from my cigarette lighter. I planned to relocate my plate and attach the blower in its place.
Then I thought .... WHY ?
I don't have the link right in front of me, but something like this has been used to great effect in semis using a compressed air system that channels air into a tighter wake.
( If you are really interested, I can try and find it )